Polymers with photoluminescent centers in their structure are of great interest in the field of bioimaging and could be artificial analogs to green fluorescent protein (GFP) from jellyfish [1]. Along with intrinsic photoluminescence, jellyfish also demonstrate self-healing of their organs, which allow the creatures to survive in aquatic environments [2]. Polymer metal complexes (PMCs) of europium(III) and terbium(III) could be artificial analogs to GFP due to their excellent luminescent properties (Tb³⁺ and Eu³⁺) and to the bioinertness of PDMS.

Europium(III) and terbium(III)-containing 2,2'-bipyridine-6,6'-dicarboxamide-co-polydimethylsiloxanes (Eu-Bipy-PDMS and Tb-Bipy-PDMS) [3] and their low-molecular complexes [Tb(BDCA)₂(H₂O)]Cl₃ and [Eu(BDCA)₂(H₂O)]Cl₃ [4] were synthetized by polycondensation and complexation reactions. The structure of the obtained complexes was confirmed by NMR, IR spectroscopy, and XRD analysis. A tensile property study was carried out on a Shimadzu EZ-L-5kN testing machine (RT, constant stretching rate of 10 mm∙min^–1, sample shape ISO 37 type 3). Photoluminescence spectra and quantum yields (QYs) were studied using a HORIBA Fluorolog-3 spectrofluorometer with an integrating sphere (101 mm in diameter) at RT.

Eu-Bipy-PDMS and Tb-Bipy-PDMS show QYs of 10.5% and 18.5%. The PMCs' structure enables the formation of coordinatively saturated complexes of lanthanide ions and provides good tensile properties to Eu-Bipy-PDMS (1.55 MPa, 185%) and Tb-Bipy-PDMS (1.48 MPa, 190%). The self-healing efficiency of PMCs exceed 90%. [Tb(BDCA)₂(H₂O)]Cl₃ and [Eu(BDCA)₂(H₂O)]Cl₃ show high QYs of 36.5% and 12.6%, respectively, and can retain them after encapsulation in a semitransparent biocompatible polyethyleneglycol matrix (11.2% and 25.3%, respectively) .

Both obtained self-healing luminescent lanthanide-containing PMCs and their low-molecular analogs could be used in bioimaging and theranostics [5].

Financial support for this study was provided by St. Petersburg State University (project 94124215).

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3. Miroshnichenko, A.S. et.al. // ACS Appl. Polym. Mater. 2022, 4, 2683–2690.
4. Miroshnichenko, A.S. et.al. // Polymers 2022, 14, 5540.
5. Ranjan, S. et.al. // Nanomedicine 2015, 10, 1477–1491.